The so-called fingerprint recognition refers to performing recognition by means of the fingerprint information unique to a person's finger. There are two common fingerprint recognition methods, i.e. a capacitance fingerprint recognition method and an optical fingerprint recognition method.
In the related arts, during the capacitance fingerprint recognition: a capacitance measurement value corresponding to a sensing electrode is compared with a type determination threshold; when the capacitance measurement value is greater than or equal to the threshold, it is determined that a fingerprint recognition result corresponding to the sensing electrode is a first type (it may be a fingerprint ridge or a fingerprint valley according to a structure of the capacitor), whereas when the capacitance measurement value is smaller than the threshold, it is determined that the fingerprint recognition result corresponding to the sensing electrode is a second type that is opposite to the first type.
In such fingerprint recognition method, the capacitance detection value corresponding to the sensing electrode that corresponds to the fingerprint valley is very close to the capacitance detection value corresponding to the sensing electrode that corresponds to the fingerprint ridge. That is, an average capacitance detection value corresponding to the sensing electrode that corresponds to the fingerprint valley is A, whereas an average capacitance detection value corresponding to the sensing electrode that corresponds to the fingerprint ridge is A is A+Δ (Δ is a very small value). In the fingerprint recognition method based on an absolute capacitance measurement value in the related arts, the above threshold generally is A+Δ/2.
Once the measurement deviation is affected by factors such as the environment to some extent, a fingerprint type recognition error may occur in the above-mentioned fingerprint recognition method.
For example, it is assumed that, when the sensing electrode corresponds to the fingerprint valley, an actual capacitance value of a capacitor corresponding to the sensing electrode is A+Δ/4, and a measurement deviation is Δ/3. As a result, when the sensing electrode corresponds to the fingerprint valley, the capacitance detection value corresponding to the sensing electrode is A+Δ/4+Δ/3=A+7Δ/12. Thus, in the above fingerprint recognition criteria, since the capacitance detection value (A+7Δ/12) corresponding to the sensing electrode is greater than the type determination threshold (A+Δ/2), it is determined that the fingerprint recognition result is the fingerprint ridge, and thereby a fingerprint type recognition error occurs.